Multi-Beam Sample Topography Mapping for Focus Control
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Solution Overview
Problem
Existing assessment systems using multiple charged particle beams face challenges in accurately focusing beams over large Field of View (FoV), which affects the quality of focus and throughput.
Innovation Solution
The proposed assessment apparatus includes a sample support, a charged particle device to project a beam grid of charged particle beams, and a control system that controls the sample support and charged particle device to scan the beam grid and generate a sample surface topographical map, allowing for improved focus control and positioning of the sample.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large Field of View (FoV) is used to increase throughput, then more beams can be projected simultaneously onto the sample, but it becomes challenging to focus beams accurately over such large FoVs
Solution Approach 1:
The system divides the large Field of View into multiple smaller regions by using multiple independent beam columns, each capable of focusing its beams accurately on its assigned region. This segmentation allows the system to maintain high focus accuracy in each local area while collectively covering a large FoV to achieve high throughput.
Solution Approach 2:
The system dynamically adjusts the focal plane position for each beam column based on the local topography of the sample surface. By continuously adapting the focus position to match the sample's surface variations, the system maintains accurate focus across the entire large FoV even as the sample surface varies in height and orientation.
2Productivity
If multiple charged particle beams are projected simultaneously onto a large area of the sample surface, then throughput is increased, but the quality of focus deteriorates due to the difficulty of maintaining accurate focus over large distances and areas
Solution Approach 1:
The system uses proximity sensors to detect the actual position and topography of the sample surface, then feeds this information back to the control system. The control system adjusts the focal plane position of each beam column based on this feedback, ensuring that all beams maintain accurate focus on the sample surface despite variations in sample position and topography.
Solution Approach 2:
The system changes the focal plane position parameter for each beam column dynamically, adjusting it to match the local sample surface characteristics. This parameter adjustment allows each beam to be focused at the correct depth and position, maintaining high quality of focus across the entire large Field of View.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables improved control of focus and increased throughput by accurately positioning the sample and adjusting the focal plane of the charged particle beams, even over large FoV, thereby enhancing the quality of inspection and measurement.
Implementation Method 1
a charged particle device configured to project a beam grid of a plurality of charged particle beams along a grid path of the beam grid towards the sample; a detector configured to detect signal charged particles from the sample
Data Source
AI summary
The present disclosure relates to apparatus and methods for assessing samples using a plurality of charged particle beams. In one arrangement, at least a subset of a beam grid of a plurality of charged particle beams and respective target portions of a sample surface are scanned relative to each other to process the target portions. Signal charged particles from the sample are detected to generate detection signals. A sample surface topographical map is generated that represents a topography of the sample surface by analyzing the detection signals.